Molecular dynamics simulations of fluorosilyl species impacting fluorinated silicon surfaces with energies from 0.1 to 100 eV

A better understanding of the surface interactions of energetic atomic and molecular species is needed under conditions relevant to plasma-assisted etching and deposition. In this article we describe the results of molecular dynamics (MDs) simulations of atomic Si and molecular SiF_x (x=1-3) species impacting fluorinated silicon surfaces. These impacting species might be sputtered species incident on feature surfaces with energies typically on the order of a few eV, or etch products that are ionized in the plasma and accelerated back towards the substrate surface to attain energies on the order of tens to hundreds of eV. To model both of these cases, the incident energy was varied from 0.1 to 100 eV. We performed the MD simulations to investigate the types of possible events that occur during the picosecond(s) following the impact of these reactive atomic and molecular species. Stillinger-Weber potentials were used to model the interatomic interactions [Phys. Rev. B 31, 5262 (1985); J. Chem. Phys. 88, 5123 (1988); Phys. Rev. Lett. 62, 2144 (1989); J. Chem. Phys. 92, 6239 (1990)]. We observed a variety of events in the simulated trajectories: sticking or reflection of the impacting species, reactions with surface species, sputtering of surface material, and dissociation of the impacting molecular species. The effect of surface coverage and incident angle was studied by simulating impacts onto three silicon surfaces with different amounts [monolayers (MLs)] of fluorine (0 ML F, 1 ML F, 2 ML F), and by varying the incident angle of Si atoms from 0° to 75° from the surface normal. These effects are illustrated for select cases.